A Level Physics Notes: Electricity - Capacitors in Series and Parallel
A capacitor is an electronic device that acts as a store of charge. It is typically pictured as two metal plates facing each other, with a wire connected to each, as shown below.
,
where
is
the capacitance of the capacitor in question, taken to be constant
for that capacitor.
Capacitors
in Parallel
The capacitance of capacitors in parallel is given by
Proof: Because the capacitors are in parallel the voltage across
them is the same, and the total charge on the pair is the sum of the
charges, so
(1).
and
for
each capacitor, andfor
the pair. Sub these into (1) to get
and
divide by
to
get
Because the capacitors are in series, charge that flows from one
capacitor must flow on to the other so the charge on each capacitor
is the same, and
(2).
From the three equations above we get
and
Sub
these into (2) to get
then
divide by
to
get